A moving boundary detector is being developed which will be used to follow the movement of proteins, nucleic acids, amino acids and nucleotides in free electrophoresis experiments. The detector operated at radio frequencies and detects boundaries at platinum film rings fused onto the outside of the moving boundary tube. The effects of protein concentration and of the pH, nature and ionic strength of the buffer on the mobility of bovine serum albumun (BSA) are being investigated. Temperature and pressure coefficients of mobility will also be measured. Large peaks are obtained for 0.1 wt. percent BAS in 0.01 M Tris. Present results indicate a precision of 1 percent.